Chromospheric Activity, Lithium and Radial Velocities of Single Late-Type Stars Possible Members of Young Moving Groups ⋆ ⋆⋆

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Chromospheric activity, lithium and radial velocities of single late-type stars possible members of young moving groups ⋆ ⋆⋆

D. Montes, J. López-Santiago, M.J. Fernández-Figueroa, and M.C. Gálvez Departamento de Astrof´ısica, Facultad de Ciencias F´ısicas, Universidad Complutense de Madrid, E-28040 Madrid, Spain E-mail: dmg@astrax.fis.ucm.es

Received 23 July 2001 / Accepted 26 September 2001

1. Introduction could lead to a better understanding of star formation history in the solar neighbourhood. In our previous work It has long been known that in the solar vicinity there are (Montes et al. 2000a, 2001a; Paper I) a sample of late-type several kinematic groups of stars that share the space mo- stars of previously established members and possible new tions of well-known open clusters. Eggen (1994) defined a candidates to these five young SKG have been identified. ”supercluster” (SC) as a group of stars, gravitationally un- In order to better establish the membership of these can- bound, that share the same kinematics and may occupy didate stars in the different young SKG, we have started extended regions in the Galaxy, and a ”moving group” a program of high resolution echelle spectroscopic obser- (MG) as the part of the supercluster that enters the so- vations. The spectroscopic analysis of these stars allows lar neighbourhood and can be observed all over the sky. us to obtain a better determination of their radial veloc- The origin of these stellar kinematic groups (SKG) could ity, lithium (λ6707.8 line) equivalent width , rotational be the evaporation of an open cluster, the remnants of a velocity and the level of chromospheric activity. We will star formation region or a juxtaposition of several little use all these new data to study in detail the kinematics star formation bursts at different epochs in adjacent cells (Galactic space motions (U, V , W )) of these stars, apply of the velocity field. The youngest and best-documented age-dating methods for late-type stars, and in this way SKG are: the Hyades supercluster (600 Myr) the Ursa Ma- analyse in more detail the membership of these stars in jor group (Sirius supercluster) (300 Myr), the Local As- the different SKG. sociation or Pleiades moving group (20 to 150 Myr), the We present here the results of our first spectroscopy IC 2391 supercluster (35-55 Myr), and the Castor mov- studies of a sample of 14 single late-type stars selected ing group (200 Myr) (see Montes et al. 2001b, hereafter by us in Paper I as young disk stars or possible members Paper I, and references therein). of some of the above mentioned young SKG. The high Well-known members of these SKG are mainly early- resolution echelle spectra analysed here were taken dur- type stars and few studies have been centered on late-type ing three observing runs (from 1999 to 2000) and include stars. However, the identification of a significant number all the optical chromospheric activity indicators from the of late-type population in these young SKG is extremely Ca ii H&KtoCa ii IRT lines as well as the Li i λ6707.8 important for the study of the chromospheric activity and line. In Sect. 2 we give the details of our observations and Send offprint requests to: D. Montes ⋆ data reduction. The radial velocity and Galactic space- Based on observations made with the 2.2m telescope of the velocity components (U, V , W ) determination is described German-Spanish Astronomical Centre, Calar Alto (Almer´ıa, i Spain), operated by the Max-Planck-Institute for Astronomy, in Sect. 3. The Li λ6707.8 line is analysed in Sect. 4. The Heidelberg, jointly with the Spanish National Commission for different chromospheric activity indicators are analysed in Astronomy, with the Nordic Optical Telescope (NOT), oper- Sect. 5. Individual results for each star are reported in ated on the island of La Palma jointly by Denmark, Finland, Sect. 6. Finally, in Sect. 7 the discussion and conclusions Iceland, Norway and Sweden, in the Spanish Observatorio del are given. Roque de Los Muchachos of the Instituto de Astrof´ısica de Canarias, and with the Isaac Newton Telescope (INT) operated on the island of La Palma by the Isaac Newton Group in 2. Observations and Data Reduction the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrof´ısica de Canarias. The spectroscopic echelle observations of the stars anal- ⋆⋆ Tables 1, 4, 5 also available in electronic form ysed in this paper were obtained during three observing Correspondence to: dmg@astrax.fis.ucm.es runs: D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups 3

Fig. 1. (U, V ) and (W , V ) planes (Boettlinger Diagram) for our star sample. We plot with different symbols the stars belonging to the different stellar kinematic groups. Filled symbols are stars that satisfied both of Eggen’s criteria (peculiar velocity, P V , and radial velocity, ρc), open symbols are other possible members. Big crosses are plotted in the central position of each group. The dashed line represents the boundaries that determine the young disk population as defined by Eggen (1984a, 1989).

1) 2.2m-FOCES 1999/07 ESA-MUSICOS spectrograph. This is a fibre-fed cross- This took place on 24 -29 July 1999 using the 2.2 m tele- dispersed echelle spectrograph, built as a replica of the scope at the German Spanish Astronomical Observatory first MUSICOS spectrograph (Baudrand & Böhm 1992) (CAHA) (Almer´ıa, Spain). The Fibre Optics Cassegrain and developed as part of MUlti-SIte COntinuous Spec- Echelle Spectrograph (FOCES) (Pfeiffer et al. 1998) was troscopy (MUSICOS1) project. During this observing run, used with a 20482 15µ LORAL#11i CCD detector. The a 10242 24µ TEK5 CCD detector was used, obtaining wavelength range covers from 3910 to 9075 A˚ in 84 orders. wavelength coverage from 4430 A˚ to 10225 A˚ in 73 or- The reciprocal dispersion ranges from 0.03 to 0.07 A/pixel˚ ders. The reciprocal dispersion ranges from 0.07 to 0.15 and the spectral resolution, determined as the full width A˚ and the spectral resolution (FWHM) from 0.16 to 0.30 at half maximum (FWHM) of the arc comparison lines, A.˚ ranges from 0.09 to 0.26 A.˚ The sample of late-type stars analysed in this paper 2) NOT-SOFIN 1999/11 as well as the the non-active stars used as reference stars Observations taken on 26 -27 November 1999 using the in the spectral subtraction and the radial velocity stan- 2.56 m Nordic Optical Telescope (NOT) located at the dards used in the radial velocity determinations are listed Observatorio del Roque de Los Muchachos (La Palma, in Tables 1 and 2. In Table 1 we give the observing log. Spain). The Soviet Finnish High Resolution Echelle Spec- For each observation we list date, UT and the signal to ii trograph (SOFIN) was used with an echelle grating (79 noise ratio (S/N) obtained in the Ca H&KandHα line grooves/mm), Astromed-3200 camera and a 1152×770 regions. Table 2 shows the name, HD number, and other pixel EEV P88200 CCD detector. The wavelength range stellar parameters such as the spectral type (Tsp), color covers from 3525 to 10425 A˚ in 44 orders. The recipro- indexes V –R and B–V , rotational velocity (v sin i), rota- cal dispersion ranges from 0.06 to 0.17 A/pixel˚ and the tional period (Pphot). The V –R and B–V color indexes spectral resolution (FWHM) from 0.14 to 0.32 A.˚ are obtained from the relation with spectral type given by Landolt-Börnstein (Schmidt-Kaler 1982) when individual 3) INT-MUSICOS 2000/01 values are not given in the literature. Other parameters Observations make on 18-22 January 2000 with the 2.5 m are taken from the references given in the individual re- Isaac Newton Telescope (INT) at the Observatorio del 1 Roque de Los Muchachos (La Palma, Spain) using the http://www.ucm.es/info/Astrof/MUSICOS.html 4 D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups sults of each star. The Galactic space motions (U, V , W ) given in Table 2 have been determined by us as explained in the next section. The spectra have been extracted using the standard reduction procedures in the IRAF2 package (bias subtraction, flat-field division and optimal extraction of the spectra). The wavelength calibration was obtained by taking spectra of a Th-Ar lamp. Finally, the spectra were nor- malized by a polynomial fit to the observed continuum.

3. Radial Velocities and Space Motions

Heliocentric radial velocities were determined by using the cross-correlation technique. The spectra of the program stars were cross-correlated order by order, using the rou- tine fxcor in IRAF, against spectra of radial velocity standards of similar spectral types (the stars marked with * in Tables 1 and 2) taken from Beavers et al. (1979). The velocity is derived for each order from the position of the cross-correlation peak. Radial velocity errors for each order are computed by fxcor based on the fitted peak i i height and the antisymmetric noise as described by Tonry Fig. 2. Li λ6707.8 line equivalent width, EW (Li ) versus & Davis (1979). In Table 3 we list, for each spectrum, the spectral type for our star sample. Symbols are as in Fig. 1. Dashed line represent the upper envelope of EW (Li i) heliocentric radial velocities (Vhel) and their associated errors (σ ) obtained as weighted means of the individual observed in the young open cluster IC 2602; solid lines are V i values deduced for each order. The orders including chro- the upper and lower envelopes of EW (Li ) in the Pleiades mospheric features and prominent telluric lines have been and the dotted line in the Hyades. excluded when determining the mean velocity. Finally, we also list in Table 3 a mean value for each star, obtained as tion given in the literature (see Paper I) of the five young weighted mean of the individual values deduced for each SKG analysed in this work. spectrum. As in Paper I we have used as membership criteria the We have used these radial velocities together with pre- position of the stars in the velocity space (U, V , W ) and cise measurements of proper motions and parallaxes taken the Eggen’s kinematic criteria of deviation of the space from Hipparcos (ESA 1997) and Tycho-2 (Høg et al. 2000) motion of the star from the convergent point (peculiar ve- Catalogues, to calculate the Galactic space-velocity com- locity, P V ) and comparison between the observed and cal- ponents (U, V , W ) in a right-handed coordinated system culated (ρc) radial velocities. Using these criteria we have (positive in the directions of the Galactic center, Galactic considered PW And, V368 Cep, V383 Lac, EP Eri, DX rotation, and the North Galactic Pole, respectively). We Leo, GJ 211, HD 77407, and EK Dra as possible members have modified the procedures in Johnson & Soderblom of the Local Association (LA); V834 Tau, π1 UMa, and (1987) to calculate U, V , W , and their associated errors. GJ 503.2 as possible members of the Ursa Major group The original algorithm (which requires epoch 1950 coor- (UMa); GJ 577 as a possible member of the Hyades su- dinates) is adapted here to epoch J2000 coordinates in percluster (HS); GJ 3706 as a possible member of IC 2391 the International Celestial Reference System (ICRS). The supercluster; and LQ Hya as another young disk (YD) uncertainties of the velocity components have been ob- star. More details about the membership of these stars tained using the full covariance matrix in order to take are given in the individual results of each star. into account the possible correlation between the astrometric parameters. We have used the correlation coeffi- cients provided by Hipparcos (ESA 1997). The obtained 4. The Li i λ6707.8 line values are given in Table 2 and the (U, V ) and (W , V ) The resonance doublet of Li i at λ6707.8 A˚ is an important planes (Boettlinger Diagram) are plotted in Fig. 1. In this diagnostic of age in late-type stars since it is destroyed eas- figure we have also plotted (big crosses) the central posi- ily by thermonuclear reactions in the stellar interior. This 2 IRAF is distributed by the National Optical Observatory, line is included in our echelle spectra in all the observing which is operated by the Association of Universities for Re- runs. At this spectral resolution and with the rotational − search in Astronomy, Inc., under contract with the National velocity (v sin i > 8 km s 1) of the observed stars the Science Foundation. Li i line is blended with the nearby Fe i λ6707.41 A˚ line. D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups 5

Table 1. Observing log

Name 2.2m-FOCES 1999/07 NOT-SOFIN 1999/11 INT-MUSICOS 2000/01

Day UT S/N S/N Day UT S/N S/N Day UT S/N S/N (H&K) (Hα) (H&K) (Hα) (H&K) (Hα) LA

PW And 25 04:09 23 123 26 20:24 25 107 ” 26 00:57 19 110 27 21:29 20 155 ” 27 02:25 13 85 ” 28 00:57 15 76 ” 29 03:01 21 122 ” 30 01:57 20 130 V368 Cep 25 01:00 31 168 27 20:53 13 132 ” 26 00:12 16 167 ” 27 04:08 11 80 ” 28 02:14 26 179 ” 29 00:50 16 188 ” 30 00:42 30 224 V383 Lac 25 00:20 28 130 25 03:45 26 128 ” 25 23:48 11 96 ” 27 02:02 15 83 ” 28 00:33 16 77 ” 29 00:03 17 120 ” 29 23:58 16 112 EP Eri 26 22:27 23 151 ” 27 23:49 27 231 DX Leo 27 05:45 13 168 19 04:11 - 138 ” 28 06:17 37 215 21 04:58 - 139 ” 23 04:00 - 100 GJ 211 23 02:16 - 119 HD 77407 21 04:36 - 171 ” 23 03:43 - 102 EK Dra 20 07:10 - 121 ” 23 07:16 - 61 UMa

V834 Tau 27 01:49 14 132 23 01:13 - 56 ” 28 02:25 18 183 - π1 UMa 28 06:47 29 284 21 04:30 - 110 ” 23 03:34 - 94 GJ 503.2 23 06:14 - 68 Others

LQ Hya (LA) 27 06:12 12 104 21 04:01 - 123 ” 28 07:03 15 164 23 02:29 - 108 GJ 577 (HS) 25 20:19 17 89 ” 27 20:16 18 78 ” 29 19:57 26 125 GJ 3706 (IC 2391) 21 06:35 - 110 Ref. Stars

107 Psc 27 04:29 41 212 GJ 706 25 00:44 37 263 ” 25 20:07 35 176 GJ 758 * 26 00:33 43 195 HR 8088 26 00:45 43 226 GJ 639 28 22:26 29 148 GJ 679 25 22:00 39 156 β Oph * 24 23:48 31 182 ” 25 19:51 25 222 ” 25 19:55 25 268 ” 27 20:02 22 164 ” 28 19:57 39 332 ” 28 20:01 42 327 ” 29 19:46 32 314 61 Cyg A 30 00:22 43 367 61 Cyg B 30 00:31 32 336 HR 7949 26 04:39 23 235 26 20:16 42 180 HR 166 * 29 04:37 51 263 26 22:50 31 102 22 20:17 - 71 ” 27 22:52 43 162 HR 222 * 26 23:06 27 119 HR 8832 27 20:29 36 228 β Gem * 19 01:25 - 283 ” 21 03:35 - 149 Sun 23 07:53 - 268 6 D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups

Table 2. Stellar parameters

Name HD/BD Tsp V –R B–V v sin i Pphot U ± σU V ± σV W ± σW − − − − (km s 1) (days) (kms 1) (kms 1) (kms 1) LA

PW And HD 1405 K2V 0.74 1.00 23.4 1.75 -5.42±0.33 -28.69±0.63 -17.94±0.74 V368 Cep HD 220140 K1V 0.61 0.87 16.1 2.74 -10.16±0.25 -23.48±0.16 -5.45±0.10 V383 Lac BD+48 3686 K1V 0.69 0.83 19.8 2.42 -7.06±1.43 -22.19±0.34 -3.90±0.86 EP Eri HD 17925 K1V 0.69 0.86 6.2 6.85 -15.01±0.10 -21.80±0.18 -8.68±0.11 DX Leo HD 82443 K0V 0.64 0.78 6.2 5.377 -9.91±0.15 -22.83±0.36 -5.61±0.23 GJ 211 HD 37394 K1V 0.69 0.84 4.0 10.86 -12.89±0.23 -23.35±0.27 -14.55±0.18 HD 77407 BD+38 1993 G0 0.50 0.61 7.0* -10.10±0.30 -23.91±0.70 -7.12±0.38 EK Dra HD 129333 G1.5V 0.52 0.59 17.3 2.787 -7.25±0.32 -29.07±0.42 -4.65±0.35 UMa

V834 Tau HD 29697 K4V 0.91 1.09 9.5 3.936 5.71±0.31 -3.60±0.09 -21.04±0.37 π1 UMa HD 72905 G1.5V 0.52 0.62 9.7 4.68 11.24±0.09 -0.10±0.10 -10.99±0.09 GJ 503.2 HD 115043 G2V 0.53 0.67 7.5 14.52±0.26 2.19±0.21 -8.08±0.27 Others

LQ Hya HD 82558 K2V 0.64 0.91 25 1.66 -20.36±0.35 -5.45±0.17 -9.28±0.28 GJ 577 HD 134319 G5 0.54 0.68 4.448 -32.45±1.05 -13.59±0.35 -2.82±0.20 GJ 3706 HD 105631 K0V 0.64 0.80 4.5 -28.26±0.86 -22.43±0.61 -7.55±1.93

Ref. Stars

107 Psc HD 10476 K1V GJ 706 HD 166620 K2V GJ 758 * HD 182488 G8V HR 8088 HD 201196 K2IV GJ 639 HD 151877 K7V GJ 679 HD 159222 G5V β Oph * HD 161096 K2III 61 Cyg A HD 201092 K5V 61 Cyg B HD 201092 K7V HR 7949 HD 197989 K0III HR 166 * HD 3651 K0V HR 222 * HD 4628 K2V HR 8832 HD 219134 K3/4V β Gem * HD 62509 K0III Sun - G2V

We have corrected the total measured equivalent width, (600 Myr) we have used the upper envelope adopted by EW (Li i+Fe i), by subtracting the EW of Fe i calcu- Soderblom et al. (1993b). lated from the empirical relationship with (B–V ) given Representative spectra in the Li i line region of the by Soderblom et al. (1990). The obtained values are given star sample are plotted in Fig. 3. As can be seen in this in Table 3 and plotted in Fig. 2 versus their spectral type. figure a prominent Li i absorption line is observed in the stars classified as possible members of the LA except In order to obtain an estimate of the ages of our GJ 211. The other LA stars have EW (Li i) between the stars we compare their EW (Li i) with those of stars in lower and upper envelope of the Pleiades (see Fig. 2), ex- well-known young open clusters of different ages. In the cept EK Dra and HD 77407 which seem to be younger EW (Li i) versus spectral type diagram (Fig. 2) we have (EW (Li i) between the upper envelopes of the Pleiades overplotted the upper envelope of the Li i EW of IC 2602 and IC 2602). The possible members of the UMa have a (10-35 Myr), the Pleiades (78-125 Myr), and the Hyades lower Li i absorption line corresponding to the greater age (600 Myr), open clusters which cover the range of ages of of the UMa group (EW (Li i) between the upper envelope the MGs studied here. For the Pleiades we adopt the up- of the Hyades and the lower envelope of the Pleiades). The per envelope determined by Neuhäuser et al. (1997) with YD stars LQ Hya have a EW (Li i) similar to the upper data from Soderblom et al. (1993b) and Garc´ıaLópez et envelope of the Pleiades. The EW (Li i) of GJ 577 is well al. (1994) and the lower envelope given by Soderblom et above the upper envelope of the Hyades, and no Li i line al. (1993b). In the case of IC 2602 we have not adopted is detected in GJ 3706. the upper envelope given by Neuhäuser et al. (1997) with data from Randich et al. (1997) and Stauffer et al. (1997) 5. Chromospheric activity indicators because they have used EW (Li i) not corrected for the EW (Fe i) and we have determined a new upper envelope The echelle spectra analysed in this paper allow us to with corrected EW (Li i) and using, in addition, new data study the behaviour of the different optical chromospheric provided by Randich et al. (2001). Finally for the Hyades activity indicators from the Ca ii H & Ktothe Ca ii IRT D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups 7

Table 3. Radial velocities and Li i EW

Name Obs. MJD Vhel ± σV Vhel ± σV EW (LiI+FeI) EW (LiI) EW (LiI) − − (km s 1) (kms 1) (mA)˚ (mA)˚ (mA)˚ LA

PW And 2.2m 99 51384.1732 -11.76 ± 0.59 -10.99 ± 0.11 290 269 271 2.2m 99 51385.0401 -11.49 ± 0.23 283 262 2.2m 99 51386.1011 -12.50 ± 0.37 292 271 2.2m 99 51387.0396 -10.51 ± 0.42 290 269 2.2m 99 51388.1258 -11.95 ± 0.26 277 256 2.2m 99 51389.0818 -11.11 ± 0.47 296 275 NOT 99 51508.8690 -9.41 ± 0.25 305 284 NOT 99 51509.9022 -10.28 ± 0.28 300 279 V368 Cep 2.2m 99 51384.0420 -16.41 ± 0.39 -16.67 ± 0.11 229 213 207 2.2m 99 51385.0085 -17.02 ± 0.19 222 206 2.2m 99 51386.1725 -16.58 ± 0.24 231 215 2.2m 99 51387.0935 -16.83 ± 0.32 225 209 2.2m 99 51388.0347 -16.74 ± 0.32 209 193 2.2m 99 51389.0296 -16.50 ± 0.32 226 210 NOT 99 51509.8749 -15.72 ± 0.38 220 204 V383 Lac 2.2m 99 51384.0141 -19.55 ± 0.49 -20.19 ± 0.12 266 249 257 2.2m 99 51384.1565 -19.51 ± 0.49 265 248 2.2m 99 51384.9920 -20.59 ± 0.22 273 256 2.2m 99 51386.0848 -19.98 ± 0.33 277 260 2.2m 99 51387.0233 -20.61 ± 0.40 273 256 2.2m 99 51388.0023 -20.02 ± 0.22 277 260 2.2m 99 51388.9987 -20.19 ± 0.36 284 267 EP Eri NOT 99 51508.9395 17.54 ± 0.11 17.54 ± 0.11 231 211 208 NOT 99 51509.9946 225 206 DX Leo NOT 99 51509.2471 8.33 ± 0.11 8.13 ± 0.08 200 184 186 NOT 99 51510.2689 8.00 ± 0.13 196 180 INT 00 51562.1797 188 172 INT 00 51564.2121 8.16 ± 0.24 196 180 INT 00 51566.1720 7.63 ± 0.24 183 167 GJ 211 INT 00 51566.0980 0.26 ± 0.17 0.26 ± 0.17 21 2 2 HD 77407 INT 00 51564.1974 4.72 ± 0.23 4.43 ± 0.17 168 160 162 INT 00 51566.1601 4.08 ± 0.25 173 165 EK Dra INT 00 51563.3055 -19.37 ± 0.48 -20.64 ± 0.33 198 189 195 INT 00 51566.3100 -21.80 ± 0.46 201 202 UMa

V834 Tau NOT 99 51509.0815 0.59 ± 0.17 0.27 ± 0.11 91 65 60 NOT 99 51510.1062 0.07 ± 0.16 86 60 INT 00 51566.0563 -0.13 ± 0.35 80 54 π1 UMa NOT 99 51510.2862 -14.87 ± 0.15 -14.45 ± 0.13 117 107 106 INT 00 51564.1889 -12.98 ± 0.33 116 106 INT 00 51566.1501 -13.82 ± 0.34 115 105 GJ 503.2 INT 00 51566.2634 -9.26 ± 0.29 -9.26 ± 0.29 101 92 92 Others

LQ Hya NOT 99 51509.2635 6.80 ± 0.41 8.26 ± 0.19 259 237 243 NOT 99 51510.3008 7.97 ± 0.29 277 255 INT 00 51564.1761 10.30 ± 0.50 255 233 INT 00 51566.1127 8.82 ± 0.37 268 246 GJ 577 2.2m 99 51384.8466 -6.45 ± 0.15 -6.48 ± 0.10 160 148 145 2.2m 99 51386.8451 -6.52 ± 0.27 165 153 2.2m 99 51388.8314 -6.49 ± 0.14 145 133 GJ 3706 INT 00 51564.2814 -2.60 ± 0.21 -2.60 ± 0.21 18 1 1 lines, formed at different atmospheric heights. As shown sity (Barden 1985) and modified by us. The inactive stars in our previous work (Montes et el. 2000b, and references used as reference stars in the spectral subtraction were ob- therein) with the simultaneous analysis of the different op- served during the same observing run as the active stars. tical chromospheric activity indicators and using the spec- Spectra of representative reference stars in the Ca ii H tral subtraction technique, it is possible to study in de- & K, Hβ, Hα, and Ca ii IRT line regions are plotted in tail the chromosphere, discriminating between the differ- Fig. 4. In Table 4 we give the excess emission equivalent ent structures: plages, prominences, flares and microflares. width (EW ) (measured in the subtracted spectra) for the ii ii The chromospheric contribution in these features has Ca H&K,Hǫ, Hδ, Hγ, Hβ, Hα, and Ca IRT (λ8498, been determined using the spectral subtraction technique λ8542, λ8662) lines, as well as the reference star used in described in detail by Montes et al. (1995; 1997; 1998, the subtraction technique for each observation. We have 2000b). The synthesized spectrum was constructed using estimated the errors in the measured EW taking into ac- the program STARMOD developed at Penn State Univer- count the typical internal precisions of STARMOD (0.5 - 8 D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups

tion of excess emission or absorption in the chromospheric lines only when these features in the difference spectrum are larger than 3σ. Errors in the chromospheric features of the blue spectral region are larger due to the lower S/N of the spectra in this region. As an indication of the accu- racy of the data, we give in Table 1 the S/N in the Ca ii H & K, and Hα line regions. The excess emission EW have been converted to absolute chromospheric flux at the stellar surface by using the calibration of Hall (1996) as a function of (B–V). In Table 5 we give the absolute flux at the stellar surface (logFS) for the lines listed in Table 4. Representative spectra in the Hα and Ca ii IRT (λ8498, λ8542) line regions of the star sample have been plotted in Figs. 5 & 6. For each star we have plotted the observed spectrum (solid-line) and the synthesized spectrum (dashed-line) in the left panel and the subtracted spectrum in the right panel. Hα emission above the continuum is detected in PW And, V834 Tau, and LQ Hya; in the rest of the stars excess Hα emission is detected in the subtracted spectra except GJ 3706. Filled-in absorption in other Balmer lines is also detected in many of the stars. Ca ii H & K emission is observed in all the stars in which these lines are included in our spectra. Emission reversal in the Ca ii IRT lines is observed in PW And, V368 Cep, V383 Lac, DX Leo, EK Dra, V834 Tau, and LQ Hya, in the rest of the stars a filled-in absorption line profile is observed.

6. Individual Results In this section we describe the individual results about stellar parameters, kinematic, lithium, chromospheric activity, and membership of the diﬀerent SKG for each star of the sample.

6.1. PW And (HD 1405) This solar neighborhood Pleiades-age K2 dwarf (Am- bruster et al. 1998) is a fast rotator with a photometric period Pphot = 1.745 days (Hooten & Hall 1990) and v sin i = 23.4 km s−1 (Fekel 1997). Strassmeier et al. (1988) listed this star as a chromospherically active binary candidate, however, Griffin (1992) found no evidence of variability in their radial velocities, indicating it is a single star. The mean radial velocity determined by us (vr = −10.99 Fig. 3. Spectra in the Li i λ6707.8 line region for our star km s−1) is very similar to the values given by Fehren- −1 sample bach & Burnage (1982) (vr = −11.5 km s ) and Griffin −1 (1992) (vr = −10.4 km s ) supporting the single nature of this star. We have found, however, small ampli- 2 km s−1 in velocity shifts, and ±5 km s−1 in v sin i), the tude radial velocity variations which follow the rotational rms obtained in the fit between observed and synthesized period (1.75 days) of the star. These variations can be spectra in the regions outside the chromospheric features associated with photospheric spots that disturb the line (typically in the range 0.01-0.03) and the standard devia- profile of this rapidly rotating star. Bidelman (1985) and tions resulting in the EW measurements. The estimated Christian et al. (2001) reported moderate Ca ii H&K errors are in the range of 10-20%. For low active stars emission and the Hα line in emission in this star. Chro- errors are larger and we have considered as a clear detec- mospheric and transition region UV emission fluxes have D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups 9

Fig. 4. Spectra of representative reference stars in the Ca ii H&K,Hβ, Hα, and Ca ii IRT lines region. 10 D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups

Fig. 5. Spectra in the Hα line region for our star sample. Observed and synthetic spectra are shown in the left panel and subtracted spectra in the right panel. D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups 11 been reported by Ambruster et al. (1998) and Wood et al. 6.3. V383 Lac (BD+48 3686) (2000). In addition, it has been detected by the ROSAT- satellite as the 2RE J001820+305 source (Pye et al. 1995; Recent spectroscopic and photometric studies of V383 Lac Kreysing et al. 1995; Thomas et al. 1998; Rutledge et al. (Mulliss & Bopp 1994; Jeffries 1995; Henry et al. 1995; 2000), and by the EUVE-satellite as the EUVE J0018+309 Fekel 1997; Osten & Saar 1998) concluded it is a single source (Malina et al. 1994; Christian et al. 2001). In the active K1V star with an age less than of the Pleiades and eight spectra of this star that we have analysed, we have with a rapid rotation. These authors report a photomet- found intense emission in the Ca ii H &K andHǫ lines, ric period Pphot = 2.42 days and v sin i ranging from 14 −1 strong Hα emission above the continuum (see Fig. 5), ex- to 20 km s . The mean radial velocity determined from −1 cess chromospheric emissions in the other Balmer lines, our seven spectra (vr = -20.19 km s ) shows no evidence and emission reversal in the Ca ii IRT lines (Fig. 6). We of variability and it is in agreement with the range of val- −1 have detected variations in the excess emission of the dif- ues (from -19.4 to -22.1 km s ) given in the literature, ferent chromospheric lines, specially in the Balmer lines. supporting the conclusion that it is a single star. Mulliss ii High Li i abundance indicative of a Pleiades-age star is & Bopp (1994) found the Hα and Ca IRT lines filled reported by Ambruster et al. (1998). The EW (Li i) = by emission. It has been detected as an extreme ultravio- 271 mA˚ we have determined confirms it is a young star. let source (Pye et al. 1995; Lampton et al. 1997). In our The space motions and all the other spectroscopic prop- spectra, which cover more than one stellar rotation, we ii erties we have analysed prove its LA membership. have found notable emission in the Ca H & K andHǫ lines, excess chromospheric emission in the Balmer lines and emission reversal in the Ca ii IRT lines. During one of 6.2. V368 Cep (HD 220140, HIP 115147) the nights a noticeable increase in the excess emission is This star is the optical counterpart of the X-ray source H detected, showing the Hα line large emission wings. This variation could be due to a small-scale flare or to the tran- 2311+77 (Pravdo et al. 1985) and has been identified as i member of the LA and classified as a post T Tauri star sit of an active region. We have determined a EW (Li ) ˚ ˚ (Chugainov et al. 1991a, 1993; Ambruster et al. 1998; Ka- = 257 mA, similar to the values of 250 and 277 mA given by Mulliss & Bopp (1994) and Jeffries (1995) respectively. hanpääet al. 1999). The spectral type of this star in the i literature ranges from G5 to K2V, but the recent photo- This high EW (Li ) (close to the upper envelope of the metric observations of Kahanpääet al. (1999) support a Pleiades) indicates it is a young star. The space motions K1V spectral type. It is a rapidly rotating and spotted and all the other spectroscopic characteristic we have analysed in this star confirm it is a member of the LA. star with a photometric period Pphot = 2.74 d (Kahanpää et al. 1999). and v sin i = 16.1 km s−1 (Fekel 1997). From our six spectra taken in July 1999 and another one taken 6.4. EP Eri (HD 17925, GJ 117, HIP 13402) in November 1999 we have determined a constant radial velocity with a mean value of -16.67 km s−1, which is This is a very nearby (8 pc), very young (high Li i abun- within the range given in the literature (15–17 km s−1, dance) active K2-type dwarf with a rotation period of 6.85 Chugainov et al. 1991a), supporting its classification as a days (Cutispoto 1992; Henry et al. 1995). The presence of constant-velocity star. Evidence of magnetic activity in- an unresolved companion in this star has been suggested cluding strong Ca ii H & K emission, IUE-, EUVE- and by Henry et al. (1995) based on the variable widths of the ROSAT-satellite detections have been reported for this photospheric absorption lines reported in the literature star (Bianchi et al. 1991; Malina et al. 1994; Pye et al. (v sin i range from 3 to 8; see Fekel (1997)). Wood et al. 1995). In our spectra we observe intense emission in the (2000) also suggest that an unresolved secondary can be Ca ii H&KandHǫ lines, strong and variable excess chro- contributing to the emission Mg ii h and k lines. However, mospheric emissions in the Balmer lines, specially in Hα no evidence or velocity variability is reported in the liter- (Fig. 5), and the Ca ii IRT lines in emission superimposed ature (Halbwachs et al. 2000) and the radial velocity we on the corresponding absorption (Fig. 6). Chugainov et al. have determined (17.5 km s−1) is in good agreement with (1991a) report a Li i λ6707.8 A˚ line stronger than the Ca i that of Beavers & Eitter (1986) 18.8 km s−1, and Henry λ 6717 A˚ line with a EW (Li i) = 288 mA.˚ In our spec- et al. (1995) 18.1 km s−1. Cutispoto et al. (2001) also tra the Li i absorption feature is also stronger than the indicate that the binary hypothesis does not seem to be Ca i line but the mean EW we have obtained after the consistent with the Hipparcos photometric data. Strong correction of the Fe i line is EW (Li i) = 207 mA˚ which Ca ii H & K emission and a filled-in Hα line have been is similar to EW (Li i) observed in Pleiades stars of this found by Pasquini et al. (1988) and Henry et al. (1995). spectral type (Fig. 2). However, this EW (Li i) is not high Chromospheric and transition region UV emission fluxes enough to consider the star as a post T Tauri star (see have been reported by Ambruster et al. (1998) and Wood the EW (Li i) vs. spectral type diagram by Mart´ın1997). et al. (2000). It is also an X-ray and EUV source (Favata Both kinematic and spectroscopic criteria indicate V368 et al. 1995; Jeffries 1995; Lampton et al. 1997). In our Cep is a bona fide member of the LA. spectra we have found Ca ii K emission and excess chro- 12 D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups mospheric emission in the Hα and the Ca ii IRT lines. has even been classified by some authors (Gershberg et al. EP Eri is a young star as indicates the strong lithium line 1999) as a flare star. Unlike EP Eri, Habing et al. (2001) detected by Cayrel de Strobel & Cayrel (1989). We have have not detected evidence of circumstellar disk in the IR measured a EW (Li i) = 208 mA,˚ similar to the 197 mA˚ (ISO 60 µm) flux of this star. Constant radial velocity has given by Favata et al. (1995) and the 205 mA˚ obtained been reported for this star with values ranging from -0.2 −1 by Jeffries (1995). Recently, additional evidence of youth to 2 km s , which are in agreement with the vr = 0.26 has been reported. An age of 80 Myr has been estimated km s−1 we have determined. In our spectrum we observe by Lachaume et al. (1999) and a IR excess (ISO 60 µm) small excess chromospheric emission in the Balmer lines has been detected in this star and attributed by Habing et and Ca ii IRT lines and a very small EW (Li i) (2.0 mA)˚ al. (2001) to a circumstellar disk (Vega-like). Ambruster in agreement with the EW (Li i) = 1.3±3.2 mA˚ reported et al. (1998) identified it as member of the LA, and the by Gaidos et al. (2000). The space motions calculated by kinematic data analysed by Cayrel de Strobel & Cayrel us are consistent with the LA but the low level of chro- (1989) show that the birth-place of this star is associated mospheric emission and very small EW (Li i) indicate it is with the Scorpio-Centaurus complex. The position in the not a young star and probably it is not a member of the (U, V) ad (U, W) planes we have determined as well as LA. the spectroscopic criteria are in agreement with its LA membership. 6.7. HD 77407 (BD+38 1993, HIP 44458)

6.5. DX Leo (HD 82443, GJ 354.1, HIP 46843) This G0 star was included in the study of the Hyades and Sirius MGs by Eggen (1986), but not identified as a This is a nearby, young and active K0 dwarf with space member of any of these MGs. It is an X-ray/EUV source motion very similar to the LA (Soderblom & Clements detected by ROSAT and EUVE (Lampton et al. 1997) 1987; Ambruster et al. 1998; Gaidos et al. 2000). Optical and also detected as a stellar radio source by Helfand et flux modulation with a period of 5.4 days attributed to al. (1999). However, it is a very little-studied star, and no cool photospheric spots have been found by Henry et al. previous determinations of radial velocity, rotation, chro- (1995), Messina et al. (1999b), and Gaidos et al. (2000). mospheric activity and lithium have been reported in the A projected rotational velocity v sin i = 6.2 is given by literature. Using our two spectra of this star we have de- Fekel (1997). DX Leo is a single star as indicates the con- termined a mean radial velocity of 4.43 km s−1, which stant radial velocity we have determined in our spectra, together with the astrometric data results in a Galactic −1 vr = 8.13 km s , and the values of vr = 8.2, 8.9, and space motion (U, V , W ) similar to the LA. Eggen’s kine- 8.25 km s−1 given by Duquennoy et al. (1991), Griffin matic criteria also confirm their membership of the LA. (1994), and Henry et al. (1995) respectively. Strong chro- Our spectra show that it is a slow rotating star (v sin i ≈ 7 mospheric and transition region line emissions have been km s−1) with a notable chromospheric excess emission in reported by Soderblom & Clements (1987), Basri et al. the Hβ, Hα, andCa ii IRT lines. The EW (Li i)=162mA˚ (1989), Ambruster et al. 1998; Strassmeier et al. (2000), we have determined lies above the upper EW (Li i) enve- and Wood et al. (2000). It is also a X-ray and EUV source lope of the Pleiades (as also reported by Wichmann & (Pye et al. 1995; Hünsch et al. 1999). In our spectra, taken Schmitt 2001), indicating that it is a very young star and in two different epochs, we have found noticeable emission therefore a probable member of the LA. in the Ca ii H & K and Ca ii IRT lines, and excess chromospheric emission in the Hα line. We have obtained a 6.8. EK Dra (HD 129333, GJ 559.1A, HIP 71631) EW (Li i) = 198 mA˚ which is within the range observed in the Pleiades and similar to the value of EW (Li i) = This nearby G1.5V spotted and very active star (Strass- 187 mA˚ given by Strassmeier et al. (2000). The space meier & Rice 1998; Strassmeier et al. 2000) was previ- motion we have determined and all the spectroscopic cri- ously identified as a member of the LA (Chugainov 1991; teria we have analysed indicate DX Leo is a young star Chugainov et al. 1991b; Soderblom & Clements 1987) and member of the LA. considered as a young solar analog (Dorren & Guinan 1994). It is a rapidly-rotating star with v sin i 17.3 km −1 6.6. GJ 211 (HD 37394, HR 1925) s and with a photometric period ranging in the literature from 2.6 to 2.8 days (Chugainov et al. 1991b; Dorren This is a nearby star classified as a possible member of & Guinan 1994; Strassmeier & Rice 1998; Messina et al. the LA (Jeffries & Jewell 1993; Gaidos et al. 2000). It is a 2001; DePasquale et al. 2001). EK Dra can be treated es- K1V slowly rotating star (Pphot = 10.86 d, and v sin i = sentially as a single star, although Duquennoy & Mayor 4.0 km s−1, Gaidos et al. 2000) but with evidence of chro- (1991) have suggested that it may be a member of a long- mospheric activity (emission in the Ca ii H&KandMg ii period (≈ 12.5 yr) binary system with radial velocity vari- −1 −1 h & k lines, Soderblom & Clements 1987) and coronal ac- ations between -21 and -32 km s and v0 = -23.1 km s . tivity (EUV and X-ray emission Hünsch et al. 1999). It Dorren & Guinan (1994) found a mean radial velocity of - D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups 13

Fig. 6. Spectra in the Ca ii IRT (8498, 8542 A)˚ line region for our star sample. Observed and synthetic spectra in the left panel and subtracted spectra in the right panel. 14 D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups

24kms−1, Fehrenbach et al. (1997) give -18 km s−1 and we s−1 (Fekel 1997) and a short rotation period (P ≈ 4.8 days) have obtained in our spectra a mean value of -20.6 km s−1. as measured by periodic light variations due to starspots High levels of magnetic activity have been detected in this by Gaidos et al. (2000) and Bochanski et al. (2001). The star: strong Ca ii H & K emission (Soderblom 1985); vari- mean radial velocity we have determined (vr = -14.45 km able UV chromospheric emission lines (Dorren & Guinan s−1) is similar to the value reported by Duquennoy et al. −1 1 1994; Saar & Bookbinder 1998); and X-ray and EUV emis- (1991) (vr = -12.66 km s ). π UMa has high levels of sion (Güdel et al. 1997; Audard et al. 2000). In our spectra chromospheric and coronal activity (Soderblom & Mayor we observe a small emission reversal in the Ca ii IRT lines 1993a, b; Dorren & Guinan 1994). A superflare (Schaefer and a notable excess emission in the Hα and Hβ lines. et al. 2000) was detected in this star in the X-ray band Strong Li i absorption has been reported previously in the by the EXOSAT satellite (Landini et al. 1986). In our literature for this star (see Wichmann & Schmitt 2001). observations we have found small excess chromospheric In our spectra we have determined a EW (Li i) of198mA,˚ emissions in the Hα, and the Ca ii IRT lines. We have de- which is between the upper envelopes of the Pleiades and termined a EW (Li i)=106mA,˚ very close to the value of IC 2602, indicating that this star is significantly younger 96 mA˚ given by Soderblom et al. (1993a). This EW (Li i) than the Pleiades open cluster. The space motion, high is intermediate between the Hyades upper envelope and level of magnetic activity, and strong Li i absorption ob- Pleiades lower envelope, corresponding to the age of the served in this star confirm that it is a member of the LA. UMa. Our new calculation of the galactic velocity components and the spectroscopic criteria above-described are in agreement with the membership of this star to the UMa. 6.9. V834 Tau (HD 29697, GJ 174, HIP 21818)

This very active K4V star was considered for some time 6.11. GJ 503.2 (HD 115043, BD+57 1425, HIP 64532) (Strassmeier et al. 1993) as candidate to chromospherically active binary. However, the constant radial veloci- This nearby G2V star is classified as a member of the ties measured by several authors (Fouts & Sandage 1986; UMa group by Eggen (1992) and Soderblom & Mayor Henry et al. 1995; Halbwachs et al. 2000) and our radial (1993a). It is a slow rotating star with v sin i = 7.5 km s−1 −1 velocity determination (vr = 0.27 km s ) indicate that (Soderblom & Mayor 1993b). Duquennoy et al. (1991) re- −1 it is a single star. Light variations were first discovered in ported a constant radial velocity (vr = -8.86 km s ) for this star by Chugainov (1981), later, Henry et al. (1995) this star, which is very similar to the value determined −1 determined a photometric period of 3.936 days and Fekel in our spectrum (vr = -9.26 km s ) confirming it is a (1997) measured a rotational velocity, v sin i = 9.5 km s−1. single star. Evidence of magnetic activity has been found Exceptional strong Ca ii H & K emission lines (Young et in the X-ray by the ROSAT (Hünsch et al. 1999) and in al. 1989), modest Hα emission above the continuum (Rut- the ultraviolet by the IUE (Soderblom & Clement 1987) ten et al. 1989; Henry et al. 1995) and Radio, X-ray and and the HST (Lamzin 2000). Moderate Ca ii H & K chro- EUV emission (Güdel 1992; Pye et al. 1995; Hünsch et al. mospheric emission is reported by Soderblom (1985). In 1999) have been detected in this star. In our spectra taken our spectra we have found a very small fill-in in the Hα at two different epochs we have found strong emission in and Ca ii IRT lines. The Galactic velocity components we the Ca ii K line, the Hα line in emission above the contin- have determined and the kinematic criteria are compatible uum with a central self-absorption, a filled-in absorption with the star being a member of the UMa. In addition, the Hβ line, and the Ca ii IRT lines in emission. Chugainov EW (Li i)of92mA˚ determined in our spectrum, which is (1991) and Eggen (1996) listed V834 Tau as a young disk similar to the value of 77 mA˚ given by Soderblom et al. star and Chugainov (1991) suggested it as a possible mem- (1993a), indicates an age intermediate between the Hyades ber of the LA. However, the Galactic velocity components and Pleiades corresponding to the UMa. All this supports we have determined indicate it is a possible member of that GJ 503.2 is a bona fide member of the UMa. the UMa. The lithium line has been detected in this star; Henry et al. (1995) give a EW (Li i) =79mA,˚ and we 6.12. LQ Hya (HD 82558, GJ 355, HIP 46816) have determined in our spectra a EW (Li i) = 60 mA.˚ This notable EW (Li i) (see Fig. 2) indicates it is a young This star is a young single K2 dwarf classified as a BY star and confirms its membership of the UMa. Dra variable (Fekel et al. 1986). It is a rapidly rotating star with v sini = 26.5 km s−1 (Donati 1999) and with 6.10. π1 UMa (HD 72905, GJ 311, HIP 42438) a photometric rotational period of 1.600881 days (Strass- meier et al. 1997). It is a very active star, as indicated by This nearby G1.5V active star, considered as proxy of the emission in several chromospheric and transition region young Sun (Bochanski et al. 2001), has been classified as a lines, even with occasional flares (see Montes et al. 1999 possible member of the UMa moving group by Soderblom and references therein). EUV and X-ray emission and X- & Clements (1987); Soderblom & Mayor (1993a); Gaidos ray flares have been detected in this star (see Covino et (1998); and Gaidos et al. (2000). It has a v sin i = 9.5 km al. 2001 and references therein). In our four spectra taken D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups 15 at two different epochs we observed strong emission in the by Duflot et al. (1995). This star is listed by Hünsch et Ca ii K line, the Hα line in emission above the continuum al. (1999) as source of X-ray detected by the ROSAT- with an intensity similar to that observed in the quiescent satellite and Strassmeier et al. (2000) found slight Ca ii spectra by Montes et al. (1999), a filled-in absorption Hβ H&K emission. In our spectrum we have found a very low line, and the Ca ii IRT lines in emission. We have deter- level of chromospheric activity (no filled-in is detected in −1 mined a mean radial velocity, vr = 8.26 km s , very close Hα and a very slight filled-in is observed in the Ca ii IRT to the mean value of 7.3 km s−1 reported by Fekel et al. lines). The Li i absorption line is practically not detected (1986), 7.5 km s−1 given by Vilhu et al. (1991), and 9.0 in our spectrum (EW (Li i)= 1.4 mA)˚ indicating it is not km s−1 by Donati et al. (1997), confirming it is a constant a young star and probably not a member of the IC 2391 radial velocity star. Eggen (1984b) suggested that LQ Hya SC, in spite of the fact that the kinematic criteria point may be a member of the HS, Fekel et al. (1986), using their out that it is a member of this SC. new radial velocity, found it should be considered only as a YD star, however, Chugainov (1991) and Ambruster et al. (1998) listed this star as a member of the LA. The U, V 7. Discussion and conclusions and W velocity components we have calculated using the astrometric data from Tycho-2 Catalogue and the radial In this paper we have used high resolution echelle spec- velocity determined by us indicate that this star is a YD troscopic observations to test the membership of 14 single star but not a member of the LA. It is, however, a young late-type stars to young stellar kinematic groups such as star as pointed out by the strong lithium absorption line the Local Association (20 - 150 Myr), Ursa Major group (EW (Li i = 234 mA)˚ reported by Fekel et al. (1986). (300 Myr), Hyades supercluster (600 Myr), and IC 2391 In our spectra we have obtained a similar mean EW (Li i supercluster (35 Myr). We have determined accurate he- i of 243 mA,˚ which is close to the upper envelope of the liocentric radial velocities, equivalent width of the Li Pleiades cluster. doublet at λ6707.8 A,˚ and the level of chromospheric activity using different indicators from the Ca ii H&Kto the Ca ii IRT lines. All these data allow us to apply both 6.13. GJ 577 (IU Dra, HD 134319, HIP 73869) kinematic (position in the (U, V) and (W, V) planes and Messina & Guinan (1998) and Messina et al. (1999a) con- Eggen’s criteria, see Paper I) and spectroscopic (chromo- i sidered this G5V star as a proxy for the young Sun and spheric activity, and EW (Li )) criteria. classified it as a probable member of the HS according Using the kinematic criteria we have classified PW with its U, V , W components and parallax. These au- And, V368 Cep, V383 Lac, EP Eri, DX Leo, GJ 211, HD thors found high levels of photospheric magnetic activity 77407, and EK Dra as possible members of the LA. The in this star and reported a photometric rotation period of EW (Li i) and level of chromospheric activity of all these 4.448 days. The mean radial velocity we have determined stars, except GJ 211, indicate ages similar to the Pleiades −1 with our three spectra (vr = -6.48 km s ) is very close or even younger than the Pleiades (HD 77407 and EK −1 to the constant radial velocity (vr = -6.38 km s ) given Dra) confirming their membership to the LA. However, by Duquennoy et al. (1991), confirming it is likely a sin- the low level of activity and the Li i line close to the limit gle star. Soderblom (1985) found moderate chromospheric of detection we have found in GJ 211 indicate an age older emission in this star. Moderate Ca ii H & K emission is ob- than the range of ages assigned to this SKG and that this served in our spectra, however, the Hǫ line is not in emis- star should be rejected as a possible member. sion. In addition, a notable filling-in is detected in the Hα V834 Tau, π1 UMa, and GJ 503.2 turn out to be possi- and Ca ii IRT lines. The behaviour of the lithium (λ6707.8 ble members of the UMa according to the kinematic crite- line) in this star has not been previously reported in the ria. The spectroscopic criteria also confirm their member- literature. We have determined in our spectra a EW (Li i) ship. We have found for these three stars a moderate level of 145 mA˚ which is well above the upper envelope of the of chromospheric activity, and a EW (Li i) between the up- Hyades and close to the lower envelope of the Pleiades (see per envelope of the Hyades and the lower envelope of the Fig 2). Even though this star could be considered as mem- Pleiades, that corresponds to the age of 300 Myr of the ber of the HS based on its position in the (U, V) plane UMa group, which is intermediate between the Pleiades and the kinematic criteria, the EW (Li i) indicates it is and Hyades. too young to be a member of the HS. The previously identified member of the LA, LQ Hya, turns out to be a YD star (i.e. space-velocity components 6.14. GJ 3706 (HD 105631, BD+41 2276, HIP 59280) inside the boundaries that determine the young disk population) but with no clear membership of any of the young This K0V star was classified as a member of the IC 2391 SKG studied here. However, the spectroscopic criteria con- supercluster by Eggen (1991). The radial velocity we have firm it is a young star with EW (Li i) similar to the upper −1 determined for this star (vr = -2.6 km s ) is in agree- envelope of the Pleiades and the Hα line in emission above −1 ment with the previous value (vr = -3.1 km s ) reported the continuum. 16 D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups

GJ 577 was previously classified as a member of the HS, and the kinematic criteria we have applied confirm this classification. However, the EW (Li i) well above the upper envelope of the Hyades that we have determined for this star indicates that it is younger than the age assigned to the HS. Even though GJ 3706 could be considered as a member of IC 2391 according to the kinematic criteria, the very small EW (Li i) we have determined in our spectrum indicates an age too old to be a member of the very young IC 2391 SKG. An additional age estimation of these stars and those for the possible late-type stars members of young SKG we have selected in Paper I can be obtained by isochrone fitting on the color-magnitude diagram. We are carrying out this kind of study in our ongoing project dedicated to the detailed study of each young SKG and the results will be addressed in forthcoming papers. Some stars have been observed at different nights and at different epochs, covering several rotational periods. The radial velocities we have determined in these spectra show no evidence of variability and are in good agreement Fig. 7. Absolute flux at the stellar surface in the Hα, and with the range of values previously reported by other au- Ca ii IRT lines versus photometric period. thors, supporting the single nature of these stars. For some of these stars (with several spectra available) we have also We have already started a program of high resolution found low level variability of the chromospheric emission, echelle spectroscopic observations of a large sample of late- which can be attributed to low level flaring (V383 Lac) or type stars (selected by us in Paper I as possible members of the rotational modulation of chromospheric active regions young SKGs) in order to carry out a spectroscopic analysis (PW And, V368 Cep). similar to that described in this paper, and in this way The stars with the highest levels of chromospheric ac- better establish their membership of different SKGs (for tivity (LQ Hya, V834 Tau, PW And) have the Hα line preliminary results of this spectroscopic survey see Montes in emission above the continuum and also have the high- et al. 2001c). est excess emissions in the Ca ii H & K and Ca ii IRT lines. These three stars are also the most rapidly-rotating Acknowledgements. We would like to thank Dr. B.H. Foing for stars of the sample with rotation period, Pphot < 2 days. allow us to use the ESA-MUSICOS spectrograph at Isaac New- When we analyse in detail the behaviour of the chromo- ton Telescope. This research has made use the of the SIMBAD spheric excess emissions with the star rotation (character- data base, operated at CDS, Strasbourg, France, and the ARI ized by their photometric period, P or their projected Database for Nearby Stars, Astronomisches Rechen-Institut, phot Heidelberg. We would also like to thank the referee S. Cata- rotational velocity, v sin i, given in Table 2) a clear trend lano for suggesting several improvements and clarifications. of increasing activity with increasing rotation is revealed. This work was supported by the Universidad Complutense de This can be seen in Fig. 7, where we have plotted the ab- Madrid and the Spanish Dirección General de Enseñanza Su- solute flux at the stellar surface (logFS) in the Hα, and perior e Investigación Cient´ıfica (DGESIC) under grant PB97- Ca ii IRT lines versus the photometric period (logPphot). 0259. This behaviour confirms that this group of young stars also follows a rotation-activity relation similar to that References observed in other kinds of active stars (see Montes et al. 1995), and in stars members of young open clusters Ambruster, C. W., Brown, A., Fekel, F. C., Harper, G. H., (see Simon 2001, and references therein). Chromospheric Fabian, D., Wood, B., & Guinan, E. F. 1998, in ASP Conf. and transition region (using UV emission lines) rotation- Ser., 154, The Tenth Cambridge Workshop on Cool Stars, activity relations have been previously reported by Am- Stellar Systems, and the Sun, eds. R.A. Donahue & J.A. bruster et al. (1998) for five of the stars of our sample. Bookbinder, CD-1205 Audard, M., Güdel, M., Drake, J. J., & Kashyap, V. L. 2000, A more detailed analysis of the relative behaviour of ApJ, 541, 396 the different diagnostics between themselves and with re- Barden, S. C. 1985, ApJ, 295, 162 spect to the main stellar parameters of some of these stars Basri, G., Wilcots, E., & Stout, N. 1989, PASP, 101, 528 including additional spectroscopic observations will be ad- Baudrand, J., & Böhm, T. 1992, A&A, 259, 711 dressed in forthcoming papers. Beavers, W. I, & Eitter, J. J. 1986, ApJS, 62, 147 D. Montes et al.: Spectroscopic analysis of single late-type stars members of young moving groups 17

Table 4. EW of the diﬀerent chromospheric activity indicators

EW (A)˚ in the subtracted spectrum Name Obs. MJD CaII CaIIIRT Ref.Star K H Hǫ Hδ Hγ Hβ Hα λ8498 λ8542 λ8662 LA

PW And 2.2m 99 51384.1732 1.78 1.17 0.31 0.27 0.29 0.47 1.39 0.49 0.63 0.52 GJ 706 2.2m 99 51385.0401 1.36 0.99 0.33 0.28 0.28 0.45 1.26 0.51 0.63 0.56 ” 2.2m 99 51386.1011 1.98 0.93 0.32 0.26 0.29 0.51 1.35 0.50 0.66 0.53 ” 2.2m 99 51387.0396 - - - 0.28 0.27 0.44 1.23 0.47 0.62 0.55 ” 2.2m 99 51388.1258 1.97 0.82 0.26 0.24 0.26 0.48 1.20 0.47 0.61 0.52 ” 2.2m 99 51389.0818 2.18 1.68 0.33 - - 0.47 1.36 0.49 0.68 0.53 ” NOT 99 51508.8690 2.43 - - - - 0.71 1.58 0.58 0.78 - HR 222 NOT 99 51509.9022 2.36 - - - - 0.71 1.54 0.53 0.91 - ” V368 Cep 2.2m 99 51384.0420 1.25 0.68 0.20 0.17 0.22 0.28 0.82 0.36 0.48 0.40 GJ 758 2.2m 99 51385.0085 - 0.65 0.25 0.14 0.16 0.27 0.77 0.36 0.48 0.40 ” 2.2m 99 51386.1725 0.87 0.59 0.20 0.17 0.14 0.23 0.85 0.34 0.48 0.40 ” 2.2m 99 51387.0935 0.97 0.61 0.19 0.20 0.18 0.27 1.00 0.37 0.49 0.42 ” 2.2m 99 51388.0347 0.93 0.65 0.23 0.08 0.08 0.28 0.64 0.32 0.43 0.39 ” 2.2m 99 51389.0296 1.23 0.78 0.29 - - 0.46 1.11 0.39 0.52 0.52 ” NOT 99 51509.8749 1.07 - - - - 0.22 0.55 0.31 0.65 - HR 166 V383 Lac 2.2m 99 51384.0141 1.36 0.71 0.21 0.06 0.09 0.21 0.59 0.40 0.52 0.43 GJ 706 2.2m 99 51384.1565 1.24 0.74 0.23 0.07 0.07 0.18 0.61 0.39 0.53 0.44 ” 2.2m 99 51384.9920 - - - 0.0 0.04 0.18 0.64 0.42 0.59 0.48 ” 2.2m 99 51386.0848 1.17 1.03 0.38 0.17 0.20 0.40 1.08 0.51 0.73 0.64 ” 2.2m 99 51387.0233 1.17 0.74 0.26 0.08 0.08 0.30 0.69 0.40 0.55 0.46 ” 2.2m 99 51388.0023 1.18 0.78 0.20 0.06 0.08 0.19 0.62 0.43 0.58 0.48 ” 2.2m 99 51388.9987 1.31 0.70 0.19 - - 0.22 0.72 0.39 0.57 0.49 ” EP Eri NOT 99 51508.9395 0.67 - - - - 0.0 0.19 0.18 0.39 - HR 166 NOT 99 51509.9946 DX Leo NOT 99 51509.2471 0.59 - - - - 0.0 0.24 0.23 0.39 - HR 166 NOT 99 51510.2689 0.76 - - - - 0.0 0.23 0.24 0.37 - ” INT 00 51562.1797 - - - - - 0.0 0.22 0.30 0.35 0.32 ” INT 00 51564.2121 - - - - - 0.0 0.26 0.25 0.36 0.33 ” INT 00 51566.1720 - - - - - 0.0 0.20 0.24 0.38 0.28 ” GJ 211 INT 00 51566.0980 - - - - - 0.0 0.04 0.12 0.18 0.12 HR 166 HD 77407 INT 00 51564.1974 - - - - - 0.07 0.25 0.18 0.27 0.26 Sun INT 00 51566.1601 - - - - - 0.03 0.19 0.20 0.23 0.23 ” EK Dra INT 00 51563.3055 - - - - - 0.23 0.58 0.39 0.45 0.46 Sun INT 00 51566.3100 - - - - - 0.22 0.63 0.36 0.47 0.44 ” UMa

V834 Tau NOT 99 51509.0815 3.62 - - - - 0.55 1.51 0.56 0.91 - HR 166 NOT 99 51510.1062 3.64 - - - - 0.50 1.29 0.74 0.95 - ” INT 00 51566.0563 - - - - - 0.55 1.35 0.40 0.55 0.44 ” π1 UMa NOT 99 51510.2862 - - - - - 0.0 0.19 0.15 0.30 - Sun INT 00 51564.1889 - - - - - 0.0 0.10 0.13 0.16 0.19 ” INT 00 51566.1501 - - - - - 0.0 0.10 0.13 0.17 0.18 ” GJ 503.2 INT 00 51566.2634 - - - - - 0.0 0.06 0.09 0.11 0.12 Sun Others

LQ Hya NOT 99 51509.2635 2.36 - - - - 0.61 1.60 0.53 0.76 - HR 222 NOT 99 51510.3008 1.88 - - - - 0.58 1.41 0.51 0.80 - ” INT 00 51564.1761 - - - - - 0.58 1.49 0.49 0.65 0.58 HR 166 INT 00 51566.1127 - - - - - 0.56 1.58 0.57 0.65 0.55 ” GJ 577 2.2m 99 51384.8466 0.33 0.22 0.0 0.0 0.0 0.0 0.20 0.23 0.28 0.28 GJ 679 2.2m 99 51386.8451 0.28 0.26 0.0 0.0 0.0 0.0 0.24 0.21 0.34 0.29 ” 2.2m 99 51388.8314 0.42 0.22 0.0 0.0 0.0 0.0 0.22 0.19 0.27 0.27 ” GJ 3706 INT 00 51564.2814 - - - - - 0.0 0.0 0.11 0.11 0.11 HR 166

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Table 5. Absolute surface ﬂux of the diﬀerent chromospheric activity indicators

−2 −1 logFS (erg cm s ) Name Obs. MJD CaII Ca II IRT K H Hǫ Hδ Hγ Hβ Hα λ8498 λ8542 λ8662 LA

PW And 2.2m 99 51384.1732 6.476 6.294 5.717 5.670 5.722 5.978 6.600 6.088 6.197 6.114 2.2m 99 51385.0401 6.360 6.222 5.745 5.686 5.707 5.959 6.557 6.106 6.197 6.146 2.2m 99 51386.1011 6.523 6.194 5.731 5.654 5.722 6.014 6.587 6.097 6.218 6.122 2.2m 99 51387.0396 - - - 5.686 5.691 5.950 6.547 6.070 6.190 6.138 2.2m 99 51388.1258 6.520 6.140 5.641 5.619 5.675 5.987 6.536 6.070 6.183 6.114 2.2m 99 51389.0818 6.564 6.451 5.745 - - 5.978 6.591 6.088 6.231 6.122 NOT 99 51508.8690 6.612 - - - - 6.157 6.656 6.161 6.290 - NOT 99 51509.9022 6.599 - - - - - 6.645 6.122 6.357 - V368 Cep 2.2m 99 51384.0420 6.582 6.318 5.786 5.722 5.844 5.972 6.511 6.043 6.168 6.089 2.2m 99 51385.0085 - 6.298 5.883 5.638 5.706 5.956 6.483 6.043 6.168 6.089 2.2m 99 51386.1725 6.425 6.256 5.786 5.722 5.648 5.886 6.526 6.018 6.168 6.089 2.2m 99 51387.0935 6.472 6.270 5.764 5.793 5.757 5.956 6.597 6.055 6.177 6.110 2.2m 99 51388.0347 6.453 6.298 5.847 5.395 5.405 5.972 6.403 5.992 6.120 6.078 2.2m 99 51389.0296 6.575 6.377 5.947 - - 6.187 6.642 6.078 6.203 6.203 NOT 99 51509.8749 6.514 - - - - 5.867 6.337 5.978 6.300 - V383 Lac 2.2m 99 51384.0141 6.699 6.416 5.887 5.347 5.530 5.913 6.412 6.116 6.230 6.147 2.2m 99 51384.1565 6.658 6.434 5.927 5.414 5.421 5.846 6.426 6.105 6.238 6.157 2.2m 99 51384.9920 - - - - 5.178 5.846 6.447 6.137 6.285 6.195 2.2m 99 51386.0848 6.633 6.578 6.145 5.799 5.877 6.193 6.674 6.222 6.377 6.320 2.2m 99 51387.0233 6.633 6.434 5.980 5.472 5.479 6.068 6.480 6.116 6.254 6.177 2.2m 99 51388.0023 6.637 6.457 5.866 5.347 5.479 5.870 6.433 6.147 6.277 6.195 2.2m 99 51388.9987 6.682 6.410 5.844 - - 5.933 6.498 6.105 6.270 6.204 EP Eri NOT 99 51508.9395 6.331 - - - - - 5.887 5.749 6.085 - NOT 99 51509.9946 DX Leo NOT 99 51509.2471 6.436 - - - - - 6.074 5.911 6.140 - NOT 99 51510.2689 6.546 - - - - - 6.056 5.929 6.117 - INT 00 51562.1797 ------6.036 6.026 6.093 6.054 INT 00 51564.2121 ------6.109 5.947 6.105 6.068 INT 00 51566.1720 ------5.995 5.929 6.129 5.996 GJ 211 INT 00 51566.0980 ------5.232 5.587 5.763 5.587 HD 77407 INT 00 51564.1974 - - - - - 5.806 6.276 5.920 6.096 6.080 INT 00 51566.1601 - - - - - 5.438 6.157 5.966 6.027 6.027 EK Dra INT 00 51563.3055 - - - - - 6.356 6.663 6.270 6.332 6.342 INT 00 51566.3100 - - - - - 6.337 6.699 6.235 6.351 6.322 UMa

V834 Tau NOT 99 51509.0815 6.655 - - - - 5.894 6.535 6.084 6.295 - NOT 99 51510.1062 6.657 - - - - 5.852 6.467 6.205 6.314 - INT 00 51566.0563 - - - - - 5.894 6.486 5.938 6.076 5.979 π1 UMa NOT 99 51510.2862 ------6.147 5.834 6.135 - INT 00 51564.1889 ------5.868 5.772 5.862 5.937 INT 00 51566.1501 ------5.868 5.772 5.888 5.913 GJ 503.2 INT 00 51566.2634 ------5.591 5.578 5.665 5.703 Others

LQ Hya NOT 99 51509.2635 6.778 - - - - 6.242 6.758 6.180 6.337 - NOT 99 51510.3008 6.679 - - - - 6.220 6.703 6.164 6.359 - INT 00 51564.1761 - - - - - 6.220 6.727 6.146 6.269 6.219 INT 00 51566.1127 - - - - - 6.205 6.753 6.212 6.269 6.196 GJ 577 2.2m 99 51384.8466 6.383 6.206 - - - - 6.104 5.979 6.064 6.064 2.2m 99 51386.8451 6.311 6.279 - - - - 6.183 5.939 6.148 6.079 2.2m 99 51388.8314 6.487 6.206 - - - - 6.145 5.896 6.048 6.048 GJ 3706 INT 00 51564.2814 ------5.576 5.576 5.576

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